Apparatus for laboratory simulation of ballistic field testing

ABSTRACT

A laboratory test apparatus which duplicates conditions existing within a weapon barrel for testing weapon barrel materials without the need for actual field firing. The apparatus includes a support for a sample of the barrel material to be tested and a spring loaded piston which simulates actual firing conditions at the sample when a test charge is fired within the test apparatus. The charges preferably are formed to be completely consumed when fired which eliminates the need to eject a casing and which facilitates automatic loading into a breech in the sample support from a revolving drum which is driven in synchronism with reciprocating breech closure and charge firing members.

United States Patent Eig et al.

APPARATUS FOR LABORATORY SIMULATION OF BALLISTIC FIELD TESTING Merrill Elg, Parsippany; John J. Scavuzzo, Wayne, both of NJ.

Inventors:

Assignee: The United States of America as represented by the Secretary of the Army Filed: Sept. 18, 1970 Appl. No.: 73,323

[451 July 18,1972

3,327,518 6/1967 Sjolin ..73/7

Primary Examiner-S. Clement Swisher Attorney-Harry M. Saragovitz, Edward J. Kelly and Herbert Berl ABSTRACT A laboratory test apparatus which duplicates conditions existing within a weapon barrel for testing weapon barrel materials without the need for actual field firing. The apparatus includes a support for a sample of the barrel material to be tested and a spring loaded piston which simulates actual firing conditions at the sample when a test charge is fired within the test apparatus. The charges preferably are formed to be completely consumed when fired which eliminates the need to eject a casing and which facilitates automatic loading into a breech in the sample support from a revolving drum which is driven in synchronism with reciprocating breech closure and charge firing members.

15 Claims, 6 Drawing Figures PATENTEU Jun 8 I972 SHEET 2 BF 2 INVENTOR. JOHN J.SCAVUZZO APPARATUS FOR LABORATORY SIMULATION OF BALLISTIC FIELD TESTING The invention described herein may be manufactured, used and licensed by or for the Government for Governmental purposes without the payment to us of any royalties thereon.

BACKGROUND AND SUMMARY OF THE INVENTION The present invention is a laboratory test apparatus which simulates ballistic field testing. It may be used in research and development work for a variety of weapons. It will be specifically described herein, however, in terms of a device for testing and evaluating various materials for use in mortar barrels or mortar barrel linings.

At present, it is customary and necessary to run extended field tests with actual weapons in order to evaluate weapon materials and designs.

This device is able to simulate in the laboratory the environment existing in a weapon barrel when a shell is actually fired. The use of this laboratory device therefore eliminates the need for field firing of the weapon on an outdoor test range and thus affords a more rapid and comprehensive evaluation of materials at a significantly reduced cost.

Accordingly, an object of the present invention is to provide an improved means for testing weapon barrels.

Another object of the present invention is to provide a rapid and inexpensive means for testing weapon barrel materials.

Another object of the present invention is to provide a means for facilitating a comprehensive testing of weapons materials in the laboratory which simulates a full scale field testing operation.

Other and further objects of the invention will be obvious upon an understanding of the illustrative embodiment about to be described, or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice.

BRIEF DESCRIPTION OF THE DRAWING A preferred embodiment of the invention has been chosen for purposes of illustration and is shown in the drawings which form a portion of the specification wherein:

FIG. 1 is a perspective view of 'a preferred embodiment of a test device in accordance with the invention;

FIG. 2 is a vertical sectional view of the device of FIG. 1;

FIG. 3 is a vertical sectional view of a portion of the charge drum taken along line 3-3 of FIG. 2;

FIG. 4 is a vertical sectional view of a preferred embodiment of a charge suitable for use with the invention;

FIG. 5 is an enlarged vertical sectional view of the apparatus showing the driver and breech closure assembly during the charge loading step; and

FIG. 6 is a vertical sectional view similar to FIG. 5 showing the position of the driver and breech closure assembly as the charge is detonated.

The test apparatus 1 comprises a test sample container 3 which holds a sample 5 of the material which is being tested. The test sample 5 is placed adjacent one end of the container 3 adjacent to a breech opening 7. The other end of the test sample container 3 has an endwall 9 having an aperture 9a in which a piston rod II is slidably mounted. The piston rod 11 is spring loaded to provide the proper simulation of the firing action by a coil spring 13 fitted on the piston rod 11 between a flange 15 and the end wall of a hollow end casing 17. The piston rod 11 has a piston 21 mounted on its inner end having a generally cylindrical end portion 23 facing the breech opening 7 and having a flared portion 24 terminating in an enlarged base 25. The piston 21 is positioned within the test sample 5 when the spring 13 is in its normal, expanded position as illustrated in FIG. 2.

The piston base 25 occupies substantially the entire crosssectional area of the material sample 5 leaving a controlled and predetermined clearance between the base 25 and the inner wall of the test sample. When the device I is used to simulate conditions existing in an 81mm mortar, for example, the clearance is approximately 0.020 inch. As will be more fully described below, this clearance is set to provide a gas velocity and thermal environment such as normally exists between a barrel and an 8lmm mortar shell. The spring 13, when at its normal rest position in the device, is preferably slightly compressed to provide a few pounds of force on the piston 21.

The breech opening 7 of sample container 3 is loaded with propellant charges 27 of a type shown in greater detail in FIGS. 3 and 4 by an actuation and firing driver 29. The charges 27 are preferably fed from pockets 31 on a revolving drum 33 mounted on base 6. Other charge loading means may be used, for example, the charges may be stacked one above the other in a vertical feed magazine and gravity fed to the breech opening 7.

The actuator and firing driver 29 is slidably mounted for reciprocating movement in the sample container 3 on the breech closure 37. This motion is provided by a suitable drive such as a drive 35 including an electric motor 30 coupled to the driver 29 by a crank 32. The drum 33 is intermittantly advanced to present a new charge 27 to the firing driver 29 and this drive may include a driven sectional worm 34 on the motor 30 shaft periodically engaging a pinion 36 on the drum support shaft 38. The actuator and firing driver 29, as powered by the drive 35, also has limited movement along the axis of the container 3 in a recess 4 in breech closure 37. As the outer end 12 of the breech closure 37 makes contact with the charge 27 on the drum 33 during its forward stroke as shown in FIGS. 2 and 5, it pushes the charge 27 into the breech 7 of the sample container 3. As this is done, a cammed surface 39 on the driver 29 contacts and moves past the lower rear edge 67 of a latch 41 which is pivotally attached to the closure 37 at pivot 70, thereby pivoting the latchs upper end 20 into a notch 43 in sample container 3 sidewall 45. This effectively locks the breech closure 37 in place.

A final forward movement of the driver 29 in recess 4 in the closure 37 after the closure 37 is locked by latch 41 causes the detonator or firing pin 47 to move through aperture 48 thereby striking and detonating charge 27. Driver 29 is now at its forwardmost position with stop 16 compressing spring 18. This is shown in FIG. 6.

The preferred charge 27 is illustrated in FIG. 4. It comprises a shaped consumable casing 49 of solvated rifle powder enclosing a series of pads 51 of propellant. Regular shell propellant pads may be used. A suitable propellant is standard United States army M-8B propellant. The use of a consumable charge for the casing 49 eliminates the need for extraction of spent cases and makes possible a relatively simple firing mechanism. A primer or initiator 53 is positioned on the end of the casing 49 in position to be struck by firing pin 47. In apparatus designed to test materials for use in an 81mm mortar barrel, a typical charge 27 is about 5 inches long and about 1.6 inches in diameter, and the required weight of M-8B propellant is about 0.2 lbs. which represents 400 five-sheet increment pads of propellant.

Expanding gases from the ignition of the charge 27 force the piston head 21 and the rod 11 forward against spring 13. In a preferred embodiment suitable for use in testing materials for mortar barrels, the pistons enlarged base will clear the end of the test sample 5 after it has been displaced about 2.8 inches. An additional 1 inch of displacement is allowed until the mo tion is halted by a stop 10a. The test sample container 3 is provided with shielded air vents 10 adjacent its endwall 9 to vent the gas at the end of the piston stroke.

During the first 2.8 inches of piston displacement the test material 5 is subjected to sonic gas velocities, thermal exposure, and pressures which represents the exact environment existing during actual firing of a shell in a regular mortar. When the piston is at its extreme forward position, the steel spring is under about lbs. of compression and will quickly return it to its rest position.

nun A..-

After the firing pin makes contact with the primer, the driver 29 is retracted by motor 35. The driver and attached firing pin 47 ride backwardly in recess 4 causing the lower front end 68 of latch 41 to ride up cam surface 38 thereby pivoting the upper end 20 downwardly out of notch 43 in sidewall 45. This unlocks the breech closure 37 and allows it to be carried back past the revolving drum 33 by the driver 29 when stop 16 or driver 29 has contacted stop 46 and can travel no further back in recess 4. When the driver 29 has returned to its original position the drum 33 is indexed to the next position bringing a fresh charge 27 into position to be loaded into breech 7.

Although the present device has been described in terms of a laboratory device to aid in the evaluation of materials for use in mortar barrels, it can be modified to accommodate other types of weapon barrels. The modifications would entail changing the dimension of the sample container 3 and piston 21 to correspond to the dimensions of the other barrels and the shells to be held therein as well as varying the amount of spring compression and strength, and the strength of the propellant charge so as to insure duplication of pressure-time histories, flame temperatures, shock patterns and heat transfer conditions which occur in various barrels when a shell is fired.

The particular arrangement of the test material in the test material holder and the determination of the barrel environment for differing weapons is set by considering the following general criterion.

A first consideration for each barrel is the flame temperature of the propellant to be used. This criterion is met in the test device in general by using the same propellants or equivalent propellants as those used in the actual field weapons. This substitution for the test device can be finalized by routine testing using thermocouples and pressure measuring probes in a modified standard weapon.

An important consideration in determining the arrangement of the test device and in particular the spring loading of the piston and the proportioning of the clearance between the piston and the test charge is based upon a pressure versus time review of the weapon being studied. These calculations are well known in the weapon designing field so that the necessary curves of gas pressure versus projectile motion and projectile velocity versus projectile motion can be obtained for the weapon to be simulated. Similarly, measurements of propellant gas pressure versus projectile position for the full scale weapon can be obtained.

A principle purpose for the above described testing procedure is to obtain a direct indication of the weapon barrel or barrel lining erosion and particularly to make erosion measurements in known critical areas. This result is obtained directly in the test device by making the test sample with the same dimensions as the critical area of the weapon barrel being studied. In the above described example involving a mortar barrel, the critical areas are known to be inner ends of the barrel so that the test samples in this case conform to the dimensions of the inner portion of the mortar being studied.

The duplication of the pressure versus time relationship in the weapon being studied, as discussed above, and the use of similar propellant changes automatically results in the creation of identical heat transfer conditions in the laboratory simulator.

It is also desirable in the simulator to substantially duplicate or simulate the weapon detonating conditions. This is done, for example, in the case of the mortar simulator discussed above by causing the detonation to occur in the aft end of the mortar tube thereby further insuring a close simulation of shock patterns and heat transfer conditions at the test sample.

It can be seen that the above described test device provides a particular advantage in the ready accessibility provided to the test sample. The test sample holder 3, for example, may be screwed ofi from the test device at the completion of the firing of a series of charges and a direct inspection and measurements may be made of the material erosion. The present full scale field testing of weapons requires a relatively complicated removal and sectioning of the tested barrel to observe the test results. Such sectioning is, of course, time consuming and expensive and also requires a termination of the testing of that particular barrel whereas test sample in accordance with the present invention may be reinserted and further tested after preliminary examinations have been made.

It is also seen that the test device of the present invention results in a considerable material saving as the tested samples may be limited to critical areas of the weapon so that the samples are relatively small and may be fabricated at a small fraction of the cost of manufacturing completed tubes.

As various changes may be made in the form, construction and arrangement of the parts and the method described herein without departing from the spirit and scope of the invention and without sacrificing any of its advantages, it is to be understood that all matter herein is to be interpreted as illustrative and not in a limiting sense.

Having thus described our invention, we claim:

1. An apparatus for creating a laboratory simulation of firing of a ballistic device, comprising:

holding means having a hollow chamber with a test sample positioned proximate the chambers interior walls;

means for holding a propellant charge, said charge becoming fully consumed upon its detonation in the test sample holding means; and

a piston positioned within said chamber and adapted for limited movement therein, said piston producing a thermal environment within said holding means and thereby simulating a field firing of said ballistic device.

2. The apparatus as claimed in claim 1 wherein said piston positioned within said chamber has a predetermined clearance with the interior walls of said chamber.

3. An apparatus for laboratory simulation of field firings of ballistic devices comprising:

a. a container to hold a test sample of a weapon barrel;

b. a piston movably mounted on one end of the container and being normally positioned within the barrel sample;

c. means to contain a propellant charge on the other end of the container; and

d. means for detonating the charge and causing the piston to move in the container thereby producing a thermal environment within the test sample which duplicates field firing of a ballistic shell inside said barrel.

4. An apparatus as claimed in claim 3 in which the piston has a cylindrical portion facing said charge which flares outwardly to a widened base.

5. An apparatus as claimed in claim 3 which further comprises means to automatically load the charge into said container.

6. An apparatus as claimed in claim 3 in which said means to load the charge comprises a driver arm movably mounted for motion along axis of the container.

7. An apparatus as claimed in claim 6 in which the driver arm is surrounded by a breech closure member.

8. An apparatus as claimed in claim 6 in which the driver arm is movable within a recess in the closure and carries a firing pin at its end.

9. An apparatus as claimed in claim 5 in which the charges are carried to the loading means on a movable magazine.

10. An apparatus as claimed in cIaim 3 in which the cases of the propellant charges comprise solvated powder.

11. An apparatus as claimed in claim 3 in which the propellant charges comprise materials which are fully consumed upon detonation.

12. An apparatus for laboratory simulation of field firings of ballistic devices comprising:

a. a container to hold a test sample of a weapon barrel;

b. a spring loaded piston positioned on one end of the container, the head of the piston being normally situated within the barrel sample;

c. means to load a propellant charge into the other end of the container; and

to a widened base.

14. An apparatus as claimed in claim 12 in which a portion of the piston occupies substantially the entire cross-sectional area of the barrel sample.

15. An apparatus as claimed in claim 12 in which the case of the propellant charge comprises gunpowder. 

1. An apparatus for creating a laboratory simulation of firing of a ballistic device, comprising: holding means having a hollow chamber with a test sample positioned proximate the chamber''s interior walls; means for holding a propellant charge, said charge becoming fully consumed upon its detonation in the test sample holding means; and a piston positioned within said chamber and adapted for limited movement therein, said piston producing a thermal environment within said holding means and thereby simulating a field firing of said ballistic device.
 2. The apparatus as claimed in claim 1 wherein said piston positioned within said chamber has a predetermined clearance with the interior walls of said chamber.
 3. An apparatus for laboratory simulation of field firings of ballistic devices comprising: a. a container to hold a test sample of a weapon barrel; b. a piston movably mounted on one end of the container and being normally positioned within the barrel sample; c. means to contain a propellant charge on the other end of the container; and d. means for detonating the charge and causing the piston to move in the container thereby producing a thermal environment within the test sample which duplicates field firing of a ballistic shell inside said barrel.
 4. An apparatus as claimed in claim 3 in which the piston has a cylindrical portion facing said charge which flares outwardly to a widened base.
 5. An apparatus as claimed in claim 3 which further comprises means to automatically load the charge into said container.
 6. An apparatus as claimed in claim 3 in which said means to load the charge comprises a driver arm movably mounted for motion along axis of the container.
 7. An apparatus as claimed in claim 6 in which the driver arm is surrounded by a breech closure member.
 8. An apparatus as claimed in claim 6 in which the driver arm is movable within a recess in the closure and carries a firing pin at its end.
 9. An apparatus as claimed in claim 5 in which the charges are carried to the loading means on a movable magazine.
 10. An apparatus as claimed in claim 3 in which the cases of the propellant charges comprise solvated powder.
 11. An apparatus as claimed in claim 3 in which the propellant charges comprise materials which are fully consumed upon detonation.
 12. An apparatus for laboratory simulation of field firings of ballistic devices comprising: a. a container to hold a test sample of a weapon barrel; b. a spring loaded piston positioned on one end of the container, the head of the piston being normally situated within the barrel sample; c. means to load a propellant charge into the other end of the container; and d. a detonator to detonate the charge and cause the piston to move against and compress the spring thereby producing a thermal and pressure environment within the test sample which duplicates field firing of a ballistic shell inside such a barrel.
 13. An apparatus as claimed in claim 12 in which the head of the piston has a cylindrical portion which flares outwardly to a widened base.
 14. An apparatus as claimed in claim 12 in which a portion of the piston occupies substantially the entire cross-sectional area of the barrel sample.
 15. An apparatus as claimed in claim 12 in which the case of the propellant charge comprises gunpowder. 